The present invention relates to a charging paddle for use in an induction type charging apparatus for charging a battery of an electric vehicle or the like.
Conventionally, conduction type charging apparatuses and an induction type charging apparatuses have been used for charging batteries of electric vehicles. The conduction type charging apparatus has a contact type connection terminal for directly connecting an external power supply to a battery-equipped vehicle. The induction type charging apparatus has a non-contact type connection terminal for connecting a power supply with a battery through electromagnetic induction. The induction type charging apparatus is less susceptible to contact failure. In addition, induction type charging apparatuses are smaller than conduction type charging apparatuses, so the induction type charging apparatuses have drawn particular attention in recent years.
FIG. 6 illustrates a connection terminal of a conventional induction type charging apparatus. The connection terminal has a charging paddle 61 and a charging receptacle 71, which receives the charging paddle 61. The charging paddle 61 is connected to a cable 67 that extends from an external power supply station (not shown). The charging receptacle 71 is installed in an electric vehicle and is connected to a battery in the vehicle.
The charging receptacle 71 has a port 72 for receiving the charging paddle 61, a secondary core 76 contained within the charging receptacle 71, and a secondary coil 74 wound around the secondary core 76. The secondary core 76 functions as a power receiving core, while the secondary coil 74 functions as a power receiving coil. The charging paddle 61 has a paddle case 62 formed of a synthetic resin and an insertable end 63.
The insertable end 63 contains a primary core 64 and a primary coil 65 wound around the primary core 64. The primary core 64 functions as a power transmitting core, while the primary coil 65 functions as a power transmitting coil 65. For supplying power, the charging paddle 61 is plugged into the port 72 of the charging receptacle 71 to place the primary coil 65 on the secondary coil 74. Then, the power supply station passes a current (alternating current) through the primary coil 65 to induce power in the secondary coil 74.
FIG. 7 is a perspective view illustrating the primary core 64 and the secondary core 76 when the charging paddle 61 is plugged into the port 72 of the charging receptacle 71 for charging. The primary core 64 is substantially cylindrical. The secondary core 76 includes first and second core elements 73, 75. The first core element 73 has an E-shaped cross-section, and is provided with a central magnetic cylindrical protrusion 73a about which the secondary coil 74 is wound. The secondary coil 74 is accommodated in a groove formed around the protrusion 73a. The second core element 75 is plate-like and covers the groove. The core elements 73, 75 are combined such that the secondary core 76 forms a rectangular loop that surrounds a passage occupied by the insertable end 63 of the charging paddle 61. When the charging paddle 61 is fully plugged into the port 72 of the charging receptacle 71, the primary core 64 is sandwiched between the protrusion 73a of the second core 76 and the plate-like core 75 (FIG. 8). In this way, a closed magnetic circuit is formed, where the primary coil 65 is coupled with the secondary coil 74.
In the closed magnetic circuit, the power transmission efficiency between the primary coil 65 and the secondary coil 74 must be maximized. For this reason, a gap between the primary core 64 and the protrusion 73a of the secondary core 76, and a gap between the primary core 64 and the plate-like core 75 are minimized in order to minimize flux leaking from the closed magnetic circuit.
Since the gaps are minimized, it is difficult for the operator to plug the charging paddle 61 into the port 72 of the charging receptacle 71 without causing the insertable end 63 of the charging paddle 61 to interfere with the secondary core 76. Actually, the insertable end 63 interferes with a region of the secondary core 76 along which the insertable end 63 passes. In the following, this action will be described in detail.
In FIG. 7, the top surface of the distal end 66 of the paddle case 62 enters far into the charging receptacle 71 as it contacts a lower surface 77 of the core 75. Simultaneously, the bottom surface of the distal end 66 contacts an upper surface 78 of the protrusion 73a of the core 73. As the charging paddle 61 is further pressed into the charging receptacle 71, the charging paddle 61 abuts against a stopper (not shown) within the charging receptacle 71 at a position at which the primary core 64 overlaps with the protrusion 73a of the core 73. At this time, the insertion of the charging paddle 61 is complete. The insertable end 63 of the charging paddle 61 has a front, surface and a back surface that are the same, so that the insertable end 63 may be plugged into the charging receptacle 71 in either of two orientations.
FIG. 8 is a cross-sectional view illustrating the charging paddle 61 when it has been fully plugged into the charging receptacle 71. The top surface and the bottom surface of the primary core 64 are positioned within the paddle case 62 at a fixed distance from the top surface and the bottom surface of the paddle case 62, respectively. Therefore, while the charging paddle 61 is being plugged in, the top surface and the bottom surface of the primary core 64 do not interfere with the secondary core 76. When the charging paddle 61 is fully plugged in, the protrusion 73a of the core 73 of the charging receptacle 71 fits into a recess 69 in the primary core 64 of the paddle case 62.
The primary core 65 generates heat due to the charging current, and accordingly, the primary core 64 is heated. The primary coil 65 is coated with a resin coating 68, which mitigates the heat.
Since the paddle case 62 of the charging paddle 61 is thin and formed of a synthetic resin, its surface is susceptible to distortion or unevenness. This makes it difficult to maintain the thickness of the paddle case 62 at a defined dimension. Therefore, as illustrated in FIG. 9, the top surface and the bottom surface of the primary core 64 often protrude outward beyond the surface of the paddle case 62.
When the deformed charging paddle 61 is plugged into the charging receptacle 71, the primary core 64 interferes directly with the lower end 77 of the core 75 and the upper end 78 of the protrusion 73a. This peels off the coating 68 applied to the surface of the primary core 64.